An Unfortunate Swap
by Stephano1294
Summary: What happens when the apparently 'best couple in U.A' get hit by a quirk that swaps their bodies?


Izuku and Momo were leaving the restaurant they had decided to have dinner at, together as a couple, when out of nowhere a man runs past them and places his hands on the pair, creating a mist that knocked the two of them unconscious. Luckily, the criminal didn't make it far before the hero pursuing him had finally caught up. The hero soon noticed the two heroes in training lying unconscious, so he called an ambulance, and waited for the police to arrive to detain this criminal.

Izuku woke up feeling incredibly off. He felt slightly taller, had some obvious extra weight, and felt way thinner. All of these things immediately caused Izuku to panic, opening his eyes and lifting his arms. What once were arms heavy with scars and muscle, are now thin arms that have no real scarring to them. Then he then looked down and noted multiple things.

One, he has breasts. Large ones at that. Two, he has really long black hair, which keeps irritating his neck. And three, he is in the outfit which Momo wore yesterday. All these factors lead Izuku to one conclusion, and one conclusion only. He must have gotten body swapped with his girlfriend. of course, for curiosity's sake, he decided to go and check on Momo, who was hopefully occupying his own body.

Momo awoke feeling way stronger, like she could lift cars with ease stronger. And to add to that, she felt shorter and bulkier, which worried the girl. She opened her eyes just as the door opened to her room and as she glanced over to the door, saw herself standing there looking worried.

'_Wait. If I am there, then who am I?' _

As Momo thought that, she realized something about her right hand felt off, so she glanced down and realised that she was in Izuku's body. She felt something uncomfortably stiffen in her crotch, and in confusion, she glanced down and saw a bulge.

"Wait, is this normal?" Momo asked pointing down to her crotch. Izuku looked down and saw what she was pointing out, growing red with embarrassment.

"Y-Yeah, t-t-that's a n-n-n-normal r-r-react-t-tion."

"Can you tell me about it?" When Izuku shook his head, she pouted. "Why not?"

"There isn't much to tell you about other than it can and will happen randomly, although it is mainly triggered by thoughts." It was right after this that the doctor assigned to check up on Momo entered the room.

"Ah, there you are Yaoyorozu, we started panicking after you weren't seen in your bed. Are you sure you should be walking around? Do you feel any side effects of losing consciousness? Do you remember what happened before you fell unconscious?" The doctor rambled question after question to Momo, who was looking pleadingly at Izuku, but the smile on Izuku was enough of a sign, so he let himself be dragged back to the room he would be staying at.

"Let's see, I feel as fine as I should be, I mean there is a huge side effect that has happened but I wouldn't say the losing conscious part has anything to do with it, if anything us falling unconscious is because of another factor." The doctor snapped to attention at that comment.

"I guess I should tell you it involved that criminal that attacked us, his quirk swapped our bodies, I am Izuku Midoriya, not Momo Yaoyorozu, and because of that swap it must have made us lose consciousness. Maybe as a safety measure to ensure we didn't die." The doctor gave him a deadpan stare, as if thinking that there's nothing more stupid then that.

"The criminal's quirk allows him to swap personalities, not actually swap people, so it seems highly unlikely that he actually swapped you two around. I may not be a detective but I'm very certain it's likely a concussion combined with the effects of the quirk making you think you are someone else. Just get some rest, and if the problem persists then talk to the nurse at your school and have her use her quirk on ya or something like that."

"Maybe he was on a drug like trigger that amplified the effects of his quirk to the level where he actually can swap people instead of just personalities." Izuku theorized.

"Listen, not much we can do at this point, if it is that, then you two will be informed of the effects of his quirk. If it's not then it's not something that can be easily fixed by us or any medical professional, it could take a week minimum to do all the tests to figure out what is causing you two to think that you are the other."

Meanwhile with Momo…

'_Jesus christ, the hormones in a male body! I am struggling to not look at this nurse. what the hell? I thought it would have been easier to control than this! I can sorta see why Mineta is so perverted now, if the levels are roughly the same for all guys, then a male of his size would be overloaded with the hormones. I can't believe I feel sympathy towards Mineta, granted he needs to stop vocalising his perverted thoughts, but I sorta understand him now." _Momo thought while the nurse was checking the cabinets.

"So tell me, anything hurting? Do you remember what happened? All of this is standard procedure stuff I am asking, rest assured, your friend is also being taken care of, so if neither of you show any signs of a concussion then you will be released later." She stated, clearly not really paying attention.

"Nope, I remember everything leading up to the incident where that guy used his quirk on us. I hate that my date was cut short because of that prick." Momo replied swiftly, eager to get out of the hospital.

"I would like you to note down everything that happened during your time at the restaurant leading up to the moment when the villain's quirk hit you. This way we know you aren't lying to get out of here faster." The nurse handed her a tablet, which Momo got to working on right away. Izuku was also working on the same thing.

Once she deemed enough details were written down, she proceeded to hand the tablet back to the nurse, who said she would be back in around 5 to 10 minutes with the verdict. Momo was bored, so she decided to do some investigating of Izuku's body. Izuku had also finished in roughly the same time, and he did some minor investigating of Momo's own body. Neither one got too far into their search, because they were in a public place and their nurse could return anytime.

The entirety of class 1-A was sitting in the common room, awaiting their two classmates' return. When the entrance doors were opened and the class saw Aizawa enter, they knew something was happening so they paid attention.

"All right, so I know you are all worried about Midoriya and Yaoyorozu because they failed to return to their dorms last night. No need to worry, they had a short encounter with a villain as they were leaving a restaurant together. He used his quirk on the duo which knocked them unconscious, so they were at a hospital overnight and they appear fine. However, they are acting strangely, so it's likely the villain's quirk that is the cause of it" Aizawa tiredly explained, yawning after doing all that talking.

"Can we see them?" Mina asked, worried about Midori and Yaomomo.

"They were released not that long ago and should be arriving sometime soon. Classes are still on tomorrow, just because they got hit by a quirk doesn't mean they can't still do their normal classes." Aizawa said as he walked right back out of the door to sleep wherever he last placed his sleeping bag.

"What did he mean by Deku and Yaoyorozu acting weird?" Ochako questioned, curious as to how weird they will act.

"Maybe they had their personalities swapped, Midoriya is all confident and intelligent, while Yaoyorozu is a shy mess around those of the opposite gender and very jumpy? That would be weird to see." Tsuyu thought aloud.

Right after Tsuyu spoke, the doors opened and in walked Izuku and Momo, their postures identical. Both slouched and seemed embarrassed as all hell. Then Izuku(Momo) decides to speak up. "Hey, uhh, can all the girls come with me, its kinda urgent." That confused all of the girls, because Midoriya wouldn't ask all of them to come for an urgent chat. If anything, Tsuyu and Ochako alone would normally be asked.

All of them agreed, but were even more weirded out when Momo(Izuku) didn't seem to think she was included, until Midoriya tapped her shoulder. Once they were in Momo's room, Izuku decided to speak up.

"Hello, so I am sure you think I am Izuku, but that would be only half correct. I have Izuku's body and voice, but I am not Izuku. I am Momo. We got body swapped thanks to that villain encounter, so I brought you all here to help Midoriya get used to dressing as a woman, until we get turned back to normal again." Deku- no Momo said.

"Wait, hold up you are telling me you guys are in each other's bodies? Izuku is in Momo's and Momo is in Izuku's?" Kyoka asked.

"Yep. I hope we can be excused from any and all hero training until we get turned to normal, or allow us to change at the dorms. I don't want to change in the mens changing rooms because that would give all of the guys in our class a view I'd rather they not see, and I don't want to change in the girls for the opposite reasons. I don't want to see all of you girls in your underwear." He said, with a massive blush.

"Aww don't want to see us all in the nude? I'm sure if you asked none of us would mind~" Mina said as she inched closer to who they knew was Midoriya now. It was immediately confirmed to be true because he instantly locked up, spluttered, blushed even deeper, and stuttered at the teasing.

"Yep, that's definitely Midoriya, huh. So how big is he Yaomomo?" Hagakure asked, eager to know all of the info about Izuku.

"That's personal information! If Izu wants you to know, he can tell you, but that is none of my business to share!"

"Aww, damn it, was hoping to learn."

"Have you forgotten I asked you guys here to help Izuku learn how to put on a bra and to not really include either of us in discussions meant to be between girls, you all should know when I return to being myself." Momo stated.

"Alright fine. Operation help Izuku be a girl is a go!" Mina shouted in glee.

_A few hours later…_

Izuku and the girls returned to the common room, while Momo grabbed Izuku and brought him with her. Momo stopped in place and turned around and walked to grab Katsuki for this.

"Kacchan! This is very important, you have to come with me, we gotta have a discussion involving you know what."

"The fuck did you just call me high-class?" Katsuki sneered as he glared at Momo(Izuku), but he got up and followed her anyways.

The trio arrived at the teacher's lounge, Katsuki opened the door once he was filled in on what is basically going on. Momo saw All Might there and immediately went into her vice rep mode. "Sorry All Might, didn't know you were in here, we can use another room for this 'super important' discussion Izuku brought Bakugou and I along for."

"Nah high-class this is everyone necessary for now." Bakugou said.

"I'm confused." All Might stated. "Young Midoriya why are you acting like Young Yaoyorozu? And Young Bakugou, why did you refer to Young Midoriya as 'high class' when you know he isn't?"

"All Might, Momo and I got body swapped and I am worried about if our quirks got swapped with it, so I figured we tell her now just incase it wasn't. I did plan on telling her eventually anyways." All Might realized what he wanted to inform her of, and sighed.

"Young Yaoyorozu, what you are about to hear must not leave this room, got it?" All Might said as he looked her dead in the eyes.

"I promise!"

"Alright, young Midoriya has my quirk. I passed it onto him, it-"

"Hold up! You can pass on quirks?" Momo questioned intrigued at the possibilities.

"Save your questions for after as you will have plenty of them, trust me on this." Izuku said looking at his girlfriend's face.

"I can't anymore, I could only do it once, and I chose Midoriya as my successor. The quirk's name is One for All! And it is a stockpiling quirk that got combined with the ability to pass on a quirk. That ability has been carried through eight generations and it keeps getting stronger each user. I was the eighth user, Midoriya is the ninth. Now this quirk has one sole purpose, and that is to defeat it's counterpart. The quirk of All for One."

"All for One is a story for another time, but you have already met him at Kamino Ward. His quirk allows him to steal other people's quirks, use them for himself, or give them to other people. I have been the only user to win against him. Or draw against him, however you want to consider my last battle with him."

"Now, One for All appears to be doing a first of its lifetime and is allowing him to be able to use the previous user's quirks. I myself am quirkless, Midoriya is diagnosed as quirkless, however we think he has a trouble magnet quirk or something." All Might jokes. "After all, it's incredibly crazy how many villains he pulls. But the only thing you need to know is to try not to use his quirk if you can help it, as we don't need permanent damage thanks to that villain's quirk."

Just as All Might was about to continue his story, there came a knock at the door. All Might stood up and answered it. "Ah, Naomasa, what brings you here?"

"I would like to offer to Midoriya and Yaoyorozu the ability to turn back to normal," the police officer informed them. "All the villain needs to do is use his quirk on them again and the effect will be reversed."

"I'm down to change back, the less time you might be able to use One for All, the better." Izuku states while looking back at Momo.

"Wait isn't that supposed to be a secret?" Momo panics at Izuku casually mentioning something that wasn't meant to be repeated.

"A few people here know already, you are Midoriya's second person to reveal it to. Naomasa is my best friend, so I know I can trust him." All Might said as he slung an arm around Naomasa's shoulder.

"Alright. I would like to be back in my normal body again, so please take us there."

The duo ended up knocked out afterwards but they ended up back to normal thanks to the swap back. Of course, Momo was told more about the history of Izuku's quirk, and the man who took society by force, but she was happy to have been told about it.

Afterward, everything returned to normal, except Momo didn't treat Mineta as badly. Now both Izuku and Momo knew the struggles the other gender faced, if only for almost a day, but it was still plenty of time to get to know them.


End file.
